It is known to use interleaving material for separating glass sheets and protecting them from scratching and the like during shipment, storage and/or the like, particularly when stacked in a conventional manner. Herein, reference to stacked glass sheets means that a plurality of glass sheets (coated or uncoated) are stacked adjacent one another in a face-to-face relationship, irrespective of whether the major glass surfaces are disposed horizontally or vertically or in an intermediate inclined position. In other words, the stacking of glass sheets may be horizontal stacking, vertical stacking, or inclined stacking herein. Stacking of glass may occur on a pallet or the like, as known in the art.
During storage and transport, stacked glass sheets are liable to be damaged due to scratching caused by relative sliding of adjacent glass sheets, particularly when the come into contact with one another during such sliding.
It is known in the art to protect stacked glass sheets from scratching during palletized transport via the positioning of interleaving material between adjacent stacked glass sheets. For example, see U.S. Pat. Nos. 3,723,312, 4,011,359, 4,529,648 and 4,529,657, the disclosures of which are all hereby incorporated herein by reference.
A well known interleaving powder material for placement between stacked glass sheets is known as Lucite (polymethymethacrylate) (e.g., see U.S. Pat. Nos. 3,723,312 and 4,011,359). Lucite or polymethymethacrylate (PMMA) beads or particles are positioned between adjacent stacked glass sheets to protect them from scratching during storage, transport, and the like, and generally work well for their intended purpose.
However, it has been found that polymethymethacrylate beads or particles have a tendency to fall off of stacked glass sheets, especially when the glass sheets are coated with low-E (low-emissivity) coatings or the like. A low-E coating typically includes at least layer of or including silver positioned between at least first and second dielectric layers. Example non-limiting low-E coatings are disclosed in U.S. Pat. Nos. 3,649,359, 5,514,476, 5,344,718, and 6,686,050, the disclosures of which are hereby incorporated herein by reference. This tendency of polymethymethacrylate beads or particles (having a nominal size in the range of 100 to 125 microns) to fall off of (or not stick) coated glass sheets is particularly problematic when such glass sheets are raised vertically for packing on standard glass racks, pallets, or the like, and then subjected to movement and/or vibration.
It is believed that this failure of certain polymethymethacrylate beads or particles to stick to coated glass sheets is due to a lack or dissipation of static surface charge on the low-E coated surfaces of the glass sheets. For example, while static charge may be present at nominal levels on glass coated with a low-E coating, such low-E coated glass is more likely to lose its surface charge if the coating (e.g., at the edge thereof) contacts a ground path. If and when this occurs, there is a reduction or elimination in the electrostatic force which helps keep the polymethymethacrylate beads or particles on the glass (i.e., the beads or particles fall off). It will be recognized that scratching of the glass sheets becomes a problem when the protective polymethymethacrylate beads or particles tend to fall off of stacked glass sheets.
In view of the above, it is apparent that there exists a need in the art to address and solve one or more of the problems discussed above.